UPDATE (13 | Sept | 12): added some new links, my favorites are now highlighted. ADD YOUR OWN!!!!
If this list gets really long, we'll probably have to reorganize at some point. For now though, here's some resources I've collected via the Tasis Arts Wiki.
-JS

VISUAL ARTS LINKS
This is Colossal http://www.thisiscolossal.com Art + Design Blog
Art21 http://www.art21.org
Designspiration http://designspiration.net/ Provides a diverse selection of high quality, user-submitted images as a means of sharing inspiration.
Phaiden's Agenda Blog http://uk.phaidon.com/agenda/

Wooster Collective http://www.woostercollective.com - Street Art!
Urban Sketchers http://www.urbansketchers.org - This blog features sketches and often equally colorful stories behind the scenes by 100 invited artists correspondents in more than 30 countries around the world. Some are architects and illustrators, others are graphic designers, web developers, painters or educators, all sharing the same passion for drawing on location.The Teaching Collection of John Ruskin http://ruskin.ashmus.ox.ac.uk - A searchable/browsable online version of the teaching collections and catalogues assembled by John Ruskin for his Oxford Drawing Schools.
Student At Large Web Magazine http://www.studentatlarge.net/
The Drawing Research Network http://www.drawing-research-network.org.uk - The DRN is an international network of individuals and institutions who involved with improving our understanding of drawing.
New American Paintings http://www.newamericanpaintings.com - Great periodical showcasing the work of new and emerging artists.
Google Art Project - http://www.googleartproject.com/ - Take virtual tours of the world's most famous art museums using Google's street view technology.

NEW:
Arrested Motion http://arrestedmotion.com/
Art Agenda http://www.art-agenda.com/
The Art Newspaper http://www.theartnewspaper.com/
Hi-Fructose Magazine http://hifructose.com/
Boooooooom! http://www.booooooom.com/

EDUCATIONAL-ish LINKS

RadioLab http://www.radiolab.org/ THE BEST. Give it a listen if you have time. "Radiolab believes your ears are a portal to another world. Where sound illuminates ideas, and the boundaries blur between science, philosophy, and human experience. Big questions are investigated, tinkered with, and encouraged to grow. Bring your curiosity, and we'll feed it with possibility."
Brain Pickings http://www.brainpickings.org "art, design, science, technology, philosophy, history, politics, psychology, sociology, ecology, anthropology, you-name-itology."
TED Talks - http://www.ted.com/talks and the brand new TED-Ed - http://education.ted.com/
Edge.org www.edge.org

NEW:
Open Culture http://www.openculture.com/
Exp.lore http://exp.lore.com/


PHOTOGRAPHY LINKS

Aperture's Exposures Blog: http://www.aperture.org/exposures/ - A good summary of current photo happenings.
Magnum Photography: http://www.magnumphotos.com/
Atget Photography: http://www.atgetphotography.com/
Masters of Photography: http://www.masters-of-photography.com/index.html
The New Yorker's Photo Booth Blog: http://www.newyorker.com/online/blogs/photobooth
Time's Lightbox Blog: http://lightbox.time.com/
The New York Times - Lens Blog: http://lens.blogs.nytimes.com/
LensCulture: http://www.lensculture.com/
Feature Shoot: http://www.featureshoot.com/
Vivian Maier: http://vivianmaier.blogspot.com/
A recent NYTimes Article on the ongoing project processing Vivian's film:
http://lens.blogs.nytimes.com/2012/02/16/vivian-maier/
The Pixel Store: http://www.pixel-store.co.uk We recommend this site for students to order their cameras.
The Print Space: http://www.theprintspace.co.uk A London print shop favored by several of our photography students

NEW:
The Photo Brigade http://thephotobrigade.com/

DESIGN RESOURCES

Bittbox - http://www.bittbox.com/ - both textures and PS brushes. my favorites are the grunge and watercolor brushes.
Lost and Taken http://lostandtaken.com/ - high resolution textures
Corbis - http://www.corbisimages.com - stock images both commercial and royalty free.
Dafont.com - http://www.dafont.com - free fonts sortable by style / theme

TECHNOLOGY RESOURCES

Google Drive - www.drive.google.com
Why should schools be using Google Apps for Education? Check it out.
iTunes U - http://www.apple.com/education/itunes-u/
Dropbox - www.dropbox.com

Twitter - Read this article for a good summary on the benefits of using twitter for professional development and collaboration: http://www.pbs.org/mediashift/2012/09/how-twitter-is-reinventing-collaboration-among-educators272.html

In addition to facebook and twitter, here are some very active art education ning communities to check out:
http://naeaelementarydivision.ning.com NAEA elementary art teacher network
http://naea-secondary-teachers.ning.com NAEA secondary art teacher network
http://arted20.ning.com/ Art Ed. 2.0

Legal Music to use for Videos / Podcasts ( via: creative commons)
Free Music Archive
Jamendo

Blogs - several platforms to check out for those interested in starting a blog.
www.blogger.com
http://wordpress.org
http://edublogs.org

Social Bookmarking - A Web-based service where shared lists of user-created Internet bookmarks are displayed. Social bookmarking sites are a popular way to locate, classify, rank, and share online resources through the practice of tagging. Social Bookmarking Services:
http://del.icio.us
http://www.stumbleupon.com/